We continue with chapter 4 of Maseches Gittin, at Mishnah 6. The Mishnah opens with the law of one who sells his slave, and goes on to a series of enactments instituted "mipnei tikkun ha'olam," for the betterment of the world.
"HaMocher avdo l'goy o l'chutzah la'aretz - yatza ben chorin":
A person who sells his slave to a non-Jew, or who sells him to someone living outside the Land of Israel - even to a Jew - the slave goes free. This is a penalty imposed on the original owner, and he is even obligated to redeem the slave for up to ten times his value. The reason: the owner removed the slave from any possibility of keeping mitzvos. This is clear when he sold him to a non-Jew, but even when he sold him to a Jew outside the Land, the slave cannot maintain the same level of mitzvah observance.
The Gemara adds that even so, a document of release is required - a get of freedom from his original master - so that he will truly be a free man, and not merely by force of the penalty.
"Ein podin es hashvuyin yoser al k'dei d'meihen mipnei tikkun ha'olam":
Following on from the discussion of redeeming people who were sold to non-Jews, the Mishnah rules that captives are not redeemed for more than their accepted value, since there is a known market price. The reason is "mipnei tikkun ha'olam" - the general benefit of society: if people give in to an unusually high price, more Jews will be seized, because they bring a price far above market value. This is, unfortunately, an extremely relevant issue in the Land of Israel today, during the hostage crisis, and this Mishnah is quoted in that context as an issue the government has to grapple with.
"V'ein mavrichin es hashvuyin mipnei tikkun ha'olam":
Likewise, one may not act to enable captives to escape on their own, and this too is for the betterment of the world. The accepted practice in those days was to redeem captives, and if instead people would help them escape, future captives would be treated with great cruelty: they would be held in chains and shackles, whereas until now they enjoyed a certain degree of freedom. The guards would harden their treatment if it became a regular pattern that captives try to escape. Therefore the way of the Jewish community was to redeem them, and all of this is for the betterment of the world - so that other captives will not be harmed in the future.
The view of Rabban Shimon ben Gamliel:
Rabban Shimon ben Gamliel says that the reason we do not help captives escape is "mipnei takanas hashvuyin" - for the welfare of the captives who are in captivity right now, and not for the betterment of the world, which concerns future captives. In his view we do not take future captivity into account at all, but rather the fact that if the escape attempt fails, these captives will be placed in stocks and chains and will suffer themselves.
The practical difference between the two views is in a case where there is a single captive:
According to Rabban Shimon ben Gamliel: the concern is only for the captive in the present, and therefore when it is one captive and he can be smuggled out successfully - we help him escape.
According to the first Tanna: the concern is for future captives, and therefore even when it is a single captive we do not encourage him to escape; rather, we redeem him.
"V'ein lokchin sefarim tefillin u'mezuzos min hagoyim yoser al k'dei d'meihen":
The Mishnah concludes by ruling that one does not buy Torah scrolls, tefillin and mezuzos from non-Jews for more than their value. The assumption is that these items were stolen, and just as with the redemption of captives, one may not give more than the ordinary market value for them - for the betterment of the world, since otherwise people will begin stealing them and demanding exorbitant prices.
In summary: in this Mishnah we learned the law of one who sells his slave to a non-Jew or to outside the Land of Israel, that the slave goes free and requires a document of release; the enactment that captives are not redeemed for more than their value; the prohibition against helping captives escape - according to the first Tanna for the betterment of the world, and according to Rabban Shimon ben Gamliel for the welfare of the captives, along with the practical difference between them in the case of a single captive; and finally the enactment that one does not buy Torah scrolls, tefillin and mezuzos from non-Jews for more than their value.